I’m planning on removing approximately 12 feet of a load bearing wall in my house between the kitchen and dining room, and am trying to determine the weight of both the second floor above and a plaster wall on the second floor. (The attic and third floor are not supported by this wall.) Is there a standard weight per square footage used to determine the weight of the floor, wall and “people support” above?
Once I figure out the weight I can plug this number into an equation to determine what type of material to use to span the opening — I’m thinking of bolting two or three 2×8 lam beams together, but am not sure if this would provide enough strength. Additionally, I have thought about sandwiching a piece of steel in between the lam beams to give added heft.
Of course, I don’t want the second floor to fall onto the first floor (or me), so would rather err on the side of caution and overkill, rather than take a chance. Any suggestions on weight per square foot or type of material to use on this?
Replies
You local code will have a section on structural design criteria.
The loads involved include weight, wind (lateral) and seismic (acceleration). Water is the up and comer after Katrina.
To answer your question, the going rate around here for weight is 10 psf dead load plus 50 psf live load for a floor. If the wall you describe puts more dead load on the floor than 10 psf, you are required to use the actual weight of the wall (at least where I am). It's unlikely, but you never know -- maybe you've got some massive thick plaster.
To factor in and resist the other loads, you need to understand some basic principles of wood frame engineering. It ain't rocket surgery and there are plenty of good books available if you are willing to spend the time to learn.
If not, an engineer won't really cost you that much. Last time I needed the "expensive stamp" it cost less than $500. Archy would have charged $800 (BTW, those are pretty cheap prices for here so YMMV -- could also be a lot less where you are).
"Let's get crack-a-lackin" --- Adam Carolla
The code books have sizing rules for load bearing headers.
If your situation fits the sizing rules, use them.
If not, hire an engineer.
12' wall? Sure it's not a shear wall?
Every building I own has at least one interior shear wall.
"Let's get crack-a-lackin" --- Adam Carolla
For $400 I can get an enginner's written recommendation and a stamp to go with it on smaller jobs like yours. And I get to sleep at night too. Why wing it?
Brian
You mention that you can get an engineer to do the sizing for $400, aren't you supposed to do that?
I guess what I mean is that we don't have the right to just "wing it" do we?
The reason that I ask this is because on a house that I recently did a cabinet job for the GC took out a wall(defiantly load bearing) between the kitchen and living room, it has an upstairs above the kitchen. He just went to the lumber yard and bought a glue lam(the one with the 2 X 6's glued together?), he didn't consult anyone, just his good common sense(that remark was sarcasm).
I know that there was never a permit pulled for the job and he was working without liability insurance so WTF, no sense playing by the rules now!
Typically you'd have it engineered though wouldn't you? Even if you knew what it would take to hold the structure up?
Just curious
Doug
12ft ... I'd probably call the engineer. I know a good guy that's reasonable and works quick on short notice.
less than 12 ... I'd probably cypher it myself and tell the lumberyard what I'm doing. Most likely the permit stamper won't ask for an engineers stamp if what I laid out on the permit app makes sense to him too.
We do have the right ... just someone official gotta say we're making sense.
Jeff Buck Construction
Artistry In Carpentry
Pittsburgh Pa
Doug, for the most part, yes. You have to remember that most of my work is new work and I am a subcontractor. If a contractor makes a change to the plans and throws it in my lap to make it happen for them, then I call my guy at the lumberyard. They have two engineers on staff and my lumber salesman has a copy of the plans if they supplied the job. That's my SOP. Most of the time I try to steer it back to the contractor and his architect though. Why assume that responsibility? You draw it, I'll build it.
On other jobs where that particular lumberyard is not involved and I had a complicated or even somewhat complicated situation, I'd call that engineer I spoke of. If he can come out and see the situation and write up a 'prescription' in a day or less, he charges $400 for the site visit and follow up stamped prescription. Incidently, I first found him right out of the phone book, it's not like you've got to know people to get someone to look at this type of work.
What I find to be the troubling part isn't the sizing of the beams or trying to figure out what stock to use. The hard part is accurately calculating the loads and being able to wrap your head around the building as a whole and not just the affected area.
On simpler stuff, a doorway or cased opening in a 'straight forward' load bearing wall, I'm comfortable handling it on my own from experience alone. Solutions to some situations can be found in code books and span tables as well.
And I think that's the whole point. Know your limitations. People ask me stuff all the time assuming that because I know how to put a house together, I must know what to use to put a house together and it's just not that cut and dry. I'll tell you what size header to use over a 36" window devoid of any point loads, but I'm not going to stand there and size your LVL's for a 12' hole in the middle of your triple decker. Know what I mean?View Image
Thanks, to you and Buck
Doug
Besides what was said already, you also need to properly engineer the load path BELOW the removed wall, i.e. the load path from the proposed beam to the foundation. There will be concentrated loads to deal with.
DG/Builder